Why is my spot light not working?
There are two solution to this problem and they came from a scale of a scene.

After switching units to metrics (or imperial) you can see that your plate has radius over 3m, Lamp is 13m high above and size of 9cm.




You can crank up a light source Strength to something really high like 5000 and change Size accordingly.
You can scale down objects similarly to real world scales and make it a little bit physically correct. Then light won't need enormous values.